The Weed Resistance Action Group (WRAG)

The Weed Resistance Action Group (WRAG) produces guidance on pesticide resistance issues. Hosted by AHDB, this information can be used to help protect crops and the long-term efficacy of herbicides.

The AHDB-supported Resistance Action Groups (RAGs) are informal, UK-based groups consisting of experts from the Crop Protection Association (CPA) member companies, other representatives from the agrochemical industry, a range of independent organisations, including public-sector research institutes, and the Chemicals Regulation Directorate (CRD).

Find out more about WRAG

Resistance

Precision herbicide application

On 29 September 2026, the UK Weed Resistance Action Group (WRAG) and the Herbicide Resistance Action Committee (HRAC) – Europe issued a joint technical note on precision herbicide application and the risk to resistance management.

The technical note aims to:

Inform users of precision application technology of the potential herbicide resistance risks
Provide a framework for assessing risks to enable their effective use

The efficacy of any herbicide application and the numbers of survivors are key drivers of resistance that need to be considered, particularly when using precision application methods.

Download the WRAG and HRAC briefing note (Word, 150 KB)

Glyphosate resistance

At the start of 2025, the Weed Resistance Action Group (WRAG) confirmed the first three cases of glyphosate resistance in the UK (in Kent, Gloucestershire and North Yorkshire) – all in Italian rye-grass (Lolium multiflorum).

These populations demonstrated significantly reduced control from appropriate doses of glyphosate. A fourth population (Essex) also showed decreased glyphosate sensitivity.

Following widespread publicity, ten more samples of Italian rye-grass (populations from 8 farms) were identified for rapid screening, where live plant samples were potted up and sprayed with appropriate glyphosate doses by ADAS. A high risk of resistance was identified at three farms. Population offspring were subsequently tested to confirm the resistance status.

All resistance cases were from high-risk crop management situations and likely evolved from independent selections (i.e. resistance was not physically spread).

Download the latest WRAG briefing note (August 2025)

Download the initial WRAG briefing note (February 2025)

More information on glyphosate

Glyphosate resistance guidelines (short web page)
Guidelines for minimising the risk of glyphosate resistance in the UK (full PDF) (2021)
Put stewardship at the heart of glyphosate use, says WRAG (2022 news item)
Managing the resistance risk to retain long-term effectiveness of glyphosate for grass-weed control in UK crop rotations (2015–20 research)
Outlooks on Pest Management glyphosate special* (December 2018)
Herbicide resistance in amenity weed control situations (2009)

*The special features several key articles on glyphosate. It includes a paper by James Clarke, chairman of WRAG, which looks at the role of glyphosate and issues around protecting its efficacy.

For information on the development of zero and minimal herbicide regimes for controlling weeds on hard surfaces, visit sciencesearch.defra.gov.uk and search for Defra project 'PS2802'.

Resistance status

Herbicide resistance in the UK update video (2024)
Seeing the big picture on herbicide resistance (2019 CPM article)
Maps of the distribution of herbicide-resistant weeds in the UK (2016)
Current status of herbicide-resistant weeds in the UK (2014)
Status of herbicide-resistance weeds in the UK (2011)

Resistance testing

Management guidelines

Reports

Glyphosate

Managing the resistance risk to retain long-term effectiveness of glyphosate for grass-weed control in UK crop rotations (2015–20)

Black-grass (mainly)

Other grasses

Broad-leaved weeds

Herbicide Mode of Action Classification

To find a herbicide's mode of action group, use the Herbicide Resistance Action Committee (HRAC) Mode of Action Classification Map.

HRAC Mode of Action Classification 2022 Map

From 2020, the classification system aligns with the system used by the Weed Science Society of America (WSSA).

List of the current groups (with pre-2020 legacy HRAC codes in brackets)

1 (A) Inhibition of ACCase
2 (B) Inhibition of ALS
3 (K1) Inhibition of microtubule assembly
4 (O) Auxin mimics
5 (C1,2) Inhibition of photosynthesis: PS ll – Serine 264
6 (C3)Inhibition of photosynthesis: PS ll – Histidine 215
9 (G) Inhibition of EPSP synthase
10 (H) Inhibition of glutamine synthetase
12 (F1) Inhibition of PDS
13 (F4) Inhibition of DOXP synthase
14 (E) Inhibition of PPO
15 (K3) Inhibition of VLCFAs
18 (I) DHP inhibition
19 (P) Auxin transport inhibitors
22 (D) PS l electron diversion
23 (K2) Inhibition of microtubule organization
24 (M) Uncouplers
27 (F2) Inhibition of HPPD
29 (L) Inhibition of cellulose synthesis
30 (Q) Inhibition of fatty acid thioesterase
31 (R) Inhibition of serine threonine protein phosphatase
32 (S) Inhibition of solanesyl diphosphate synthase
33 (T) Inhibition of homogentisate solanesyltransferase
34 (F3) Inhibition of lycopene cyclase
0 (Z) Unknown mode of action

Example plant protection product Mode of Actions

Mode of action labelling for UK plant protection products

From 2023, all UK plant protection products will include mode of action (MoA) information on their labels.

The decision – by the Health and Safety Executive (HSE) – follows a joint statement issued by the UK Resistance Action Groups (UK-RAGs) in December 2017.

This said that greater prominence of MoA information would help farmers and agronomists make informed resistance management decisions.

Since then, members of the industry body ‘CropLife International’ have made a voluntarily commitment to include MoA icons and groups on all product labels by 2023.

Following consultation with the Crop Protection Association (CPA), the HSE announced that it will become a legal requirement to include MoA information on all UK product labels from January 2023.